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Supporting Information

Controlled processing of (Gd,Ln)2O3:Eu (Ln=Y, Lu) red phosphor

particles and compositional effects on photoluminescence

Bin Lu 1,2, Ji-Guang Li 1,* and Yoshio Sakka 1,2

(1) Materials Processing Unit, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0047

Japan

(2) Department of Materials Science and Engineering, Graduate School of Pure and Applied Sciences,

University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan

*Corresponding author

National Institute for Materials Science

Materials Processing Unit

Tel: +81-29-860-4394

E-mail: LI.Jiguang@nims.go.jp

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Figure S1. XRD peaks of the (Gd0.75Y0.2Eu0.05)2O3 precursors obtained at R=1-15.

Figure S1 shows XRD patterns of the (Gd0.75Y0.2Eu0.05)2O3 precursors obtained at R=1-15

and an aging time of 1 h. The precursor powders produced at R=1-4.5 exhibit the amorphous

phases corresponding to their spherical particle shapes (Figs. 1a-d). As R increases above 7.5,

the precursor powders improve their crystallinities and exhibit the characteristics of layered

rare-earth carbonate structures (Figs. 1e,f), although the diffraction patterns cannot be

identified by comparison with the data files of relative rare-earth compounds of known

chemical composition.

Figure S2. TG traces for the (Gd0.75Y0.2Eu0.05)2O3 precursors prepared at R=4.5 and R=7.5, respectively.

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Figure S2 shows the TG curves of two kinds of typical (Gd0.75Y0.2Eu0.05)2O3 precursors,

which have been detected to possess a chemical composition of

(Gd0.75Y0.2Eu0.05)2(CO3)3‧4H2O and (NH4)1.4(Gd0.75Y0.2Eu0.05)2(CO3)3.7‧5.6H2O, respectively

(Table 1).

The (Gd0.75Y0.2Eu0.05)2(CO3)3‧4H2O precursor decomposes to oxide via four major steps.

The first step (below 300°C) is mainly owing to dehydration and causes a weight loss (-

13.3%), which is consistent with theoretical value (-13.4%). And the weight losses of -29.8%,

-33.7% and -37.8% for the other three steps are also in accordance with the calculated weight

loss of -29.7%, -33.8% and -37.9%, respectively, which are largely due to the removal of

carbon dioxide. The decomposition processes of this precursor may be depicted as follows.

2 3 3 2 2 3 3300 300-600

2 3 2 2 2 3 2 3 600-680 680

2 3 2 3600

( ) 4 ( )

( ) ( )

dehydration decarbonation

decarbonation decarbonation

crystallite growth

Ln CO H O Ln CO

Ln O CO Ln O CO Ln O

Ln O Ln O

<

>

>

⋅ → →

→ → →

℃ ℃

℃ ℃

℃

Similarly, the decomposition processes of the (NH4)1.4(Gd0.75Y0.2Eu0.05)2(CO3)3.7‧5.6H2O

precursor were deduced as below.

dehydration and min4 1.4 2 3 3.7 2 2 3 3350 350-600

2 3 2 2 2 3 2 3 600-680 680

2 3

( ) ( ) 5.6 ( )

( ) ( )

dea ation decarbonation

decarbonation decarbonation

crystalli

NH Ln CO H O Ln CO

Ln O CO Ln O CO Ln O

Ln O

<

>

⋅ → →

→ →

℃ ℃

℃ ℃

2 3600

te growth Ln O>

→ ℃

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Figure S3. XRD patterns of the (Gd0.75Y0.2Eu0.05)2O3 precursors obtained at R=4.5 and an aging time of 3-10 h.

Figure S4. XRD patterns of (Gd,Ln)2O3:Eu precursors with the composition (Gd0.95-xYxEu0.05)2O3 (a), and (Gd0.95-xLuxEu0.05)2O3 (b).

Figure S5. Particle size distribution for the (Gd0.95Eu0.05)2O3 oxide powder.

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Figure S6. XRD patterns of the calcination products of the (Gd0.75Y0.2Eu0.05)2O3 sample.

Figure S7. Fluorescence decay behaviors of the (Gd,Ln)2O3:Eu phosphors for the 613 nm emission with the composition (Gd0.95-xYxEu0.05)2O3 (a), and (Gd0.95-xLuxEu0.05)2O3 (b).

Figure S8. Calcination temperature effect on fluorescence lifetime by taking the (Gd0.75Y0.2Eu0.05)2O3 sample as an example.

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Figure S9. Calcination temperature impact on quantum efficiency of the (Gd0.75Y0.2Eu0.05)2O3 phosphor.